Sealed jointing apparatus

ABSTRACT

Sealed jointing apparatus is for use in the connection of conduit sections, at a connection zone, especially but not exclusively telecommunication cable sections. The apparatus comprises end closure means (3) bounding the connection zone and surrounding the respective conduit sections (2). Primary seal means (9) is for location between the end closure means (3) and the conduit sections (2). Casing means (17) surrounds the end portions of the conduit sections at said connection zone, and releasable securing means (19) for sealingly securing the casing means and the closure means (3). The conductor splices in joined telecommunication cable sections can be contained in a hermetically sealed zone bounded by the end closure means (3) and the casing (17) and access can be had to the cable splices simply by releasing the releasable securing means (19) and pushing the casing (17) aside. The end closure means (3) remain in position and the primary seal means (9) are untouched. Closure of the joint simply comprises the reverse of this operation.

This invention relates to sealed jointing apparatus for use in theconnection of conduit sections at a connection zone, and morespecificially, but not necessarily, relates to a flexible hermeticallysealed cable splice/jointing point.

The present invention will find particular use in the telecommunicationsand electric industrial fields. However it can also be used in gas orwater pipe systems to enable greater flexibility in these systems.

Up until now, in telecommunication cable work with different types ofcables, such as coaxial, fibre optical and multi-core, all types ofcable closure method used the outside of the cable sheath for affixingthe seal. Therefore the outer sheath of any cable had to enter into thearea which would contain the conductor splices.

It has been well recognized within the electrical and telecommunicationfields that this type of splice closure method often failed at the pointof seal between the cable sheath and the main splice/joint sleeve,(referred to as the primary seal means) with the result that moisturecould penetrate the joint thereby causing the failure of the containedcircuits. In order to overcome these deficiences, the industries haveused additional method steps which includes (1) air pressurization ofthe system and (11) splice/joint encapsulation using resins or jellysubstances and oil filling of the splice area. These methods had thedisadvantage of being expensive and labour intensive and in most casesthe flexibility of the system was greatly impaired.

Also in this type of splice, the cables' aluminium screen had to bejumped across the splice by affixing a continuity wire to the butts ofall cables contained within.

To enter previous straight through joints, cable seals have always hadto be broken which again is expensive and time-consuming and dependingon the size and type of cable very possibly a two-man operation.

It is an object of the present invention to obviate or mitigate thesedisadvantages and to provide a jointing point which can be both quicklyentered and closed.

According to the present invention there is provided sealed jointingapparatus for use in the connection of conduit sections comprising anannular casing having open ends; spaced end closures at the end of thecasing, and defining with the casing a connection zone into whichconduit sections pass for jointing; and releasable securing means forreleasably securing at least one of the end closures to the casing; saidreleasable securing means comprising an end cap including two radiallyspaced coupling threads, one of which coupling thread threadinglyengages an external thread on the casing while the other coupling threadengages an internal thread on said one end closure whereby the casing isreleasably coupled to said one end closure.

By means of the present invention, the conductor splices in joinedtelecommunication cable sections can be contained in a hermeticallysealed zone bounded by the end closures and the casing, and access canbe had to the cable splices simply by releasing the releasable securingmeans and pushing the casing aside: the end closure means remain inposition and the primary seal means which are provided at the endclosure are untouched. Closure of the joint simply comprises the reverseof this operation. It will be understood that such access withoutbreaking the cable seal (i.e. the primary seal) provides considerableoperational and economic advantages.

In a preferred embodiment, the end closure comprises at least one andpreferably two annular members associated with a respective conduitsection. Preferably, the or each annular member includes a rigidaxially-extending auxiliary sleeve arranged such that there is formed inthe annular member a closed-bottom annular slot to receive an end partof a telecommunication cable sheath, with the sleeve located between thesheath and a core part of the cable, so that functionings of the saidprimary seal means is facilitated. The sleeve can be of metal and can beused to provide screen continuity for the telecommunication cable.

The above apparatus can be used with primary seal means which comprisesat least one gland seal on a respective annular member. Alternatively,the primary seal means may involve injection welding or heat shrinkingbetween or around the annular member and one or more respective conduitsections.

Preferably, a pair of annular members are provided, and spacer meansserve to axially space the annular members by a predetermined amount.

Embodiments of the present invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 shows a side view of a flexible hermetically sealed cablesplice/jointing apparatus or joint, part of one end of which is shownsectioned;

FIG. 2 shows a part end view of an end portion of the joint of FIG. 1with part of an end closure cut-away.

FIGS. 3A and 3B shows respectively a side view and an end view of aconductive tubular sleeve.

FIGS. 4A and 4B shows respectively a side view and an end view of alocating ring;

FIGS. 5 and 6 show isometic "exploded" views of respective ends of thejoint of FIG. 1;

FIG. 7 shows a sectional view of one end of a modified jointingapparatus according to the present invention.

Referring to FIGS. 1 and 6 of the drawings, jointing apparatus 1 servingas a jointing point for the splicing of two telecommunication cablesections 2, (one of such cable sections 2 at one end of the apparatusbeing shown in FIG. 7: the cable section at the other end is similar)comprises a cylindrical casing 17 closed at the ends by similar endplugs 3. The apparatus 1 is symmetrical about a mid-transverse medianplane and the casing 1 and the end plugs 3 define a closed chamberconstituting a connection or jointing zone for the cable sections.Referring specifically to FIG. 1, each end plug 3 comprises a pair ofaxially-extending concentric annular walls 5, 6 which are joined by aradial base 4, an outer cylindrical surface of the outer wall 5 bearingagainst an inner cyclindrical wall portion at the respective end of thecasing 17, and each end plug 3 is sealingly joined to the respective endof the casing 17 by an annular end cap 19 as will be explained in detaillater. The inner wall 6 serves to closely surround the respective cablesection 2.

An auxiliary tubular sleeve 11 (FIG. 3A, 3B) of conductive metal islocated at the inner side of wall 6, and the wall 6 is formed such thata closed bottom annular slot 12 is present between the sleeve and thewall 6. The sleeve 11 has a metal retaining ring 14 welded thereto atthe inner end, and the ring 14 is connected to the radial base 4 bymeans of socket screws 15 which extend through equi-spaced holes 13 inthe ring 14 to be received in threaded bosses 10 in the base 4: as canbe seen in FIG. 2 three bosses 10 are provided in this example.

The two end plugs 3 are axially spaced at a predetermined distance by aspacer means comprising a pair of bars, rods or tubes 16 which aresecured by means of the socket screws 15 tightened into bosses 10. Themetal sleeve 11, ring 14 and tubes 16 provide screen continuity for thecable sections. Each end of the casing 17 carries an external thread 18while the wall 5 of each plug 3 carries an internal thread 7. Theannular end cap 19 carries a pair of opposed threadings 20, 21 on axialwalls 19A, 19B which can engage with the threads 20 and 7 respectivelyso that the cap 19 can be screwed onto the threads 7, 18 to secure thecasing 17 to the end plug 3. The axial length of the spacer tubes 16 isprecisely set to permit accurate positioning of the threads, 7, 18 ateach end. The casing ends and axial walls 5 of end plugs 3 at theircontiguous ends have a series of recesses 9, and a locating ring 25 isprovided (FIGS. 4A and 4B) on one face of which ring a series ofcomplementary shaped keys 26 are provided to locate in aligned recesses9 of the cap 5 and the casing 17 for annular alignment of the threads 7,18. The space intervals between the recesses 9 and keys 26 is selectedas shown so that there is only one possible registry location. The ring25 is a laminate of a poly-vinyl-chloride (P.V.C.) washer moulded withthe keys 26 and a silicone rubber washer fitted over the keys 26 toabut, in use, against the ends of the casing 17 and wall 5 as shown inFIG. 1. the locating ring 25 in conjunction with the first seal meansensures that the cable connection zone is hermetically sealed. The endcap 3 and casing 17 are of a plastics material having a U-V stabilisersuch as carbon black as may the end plug. The cap 19 can be knurled (asshown) to facilitate tightening. A primary seal means is providedbetween the wall 6 and the respective cable section 2 to prevent ingressof moisture to the interior of the apparatus 1 and this seal means canbe in different forms depending on the use of the joint. For theapparatus shown in FIGS. 1 to 6, the primary seal means can be either aheat shrinkable collar or a jointing compound injection welded betweenthe wall 6 and the associated cable section. A hand jointing tool tofacilitate the splicing operation of the cable sections 2 can beprovided in the casing 17.

In the modified jointing apparatus shown in FIG. 7 the spacer tubes 16are located by socket screws 15 which extend radially to engage alocating ring 15A. Further, the sleeve 11 has radial portions 11A whichpass in slots in the plug base 4 and are clamped by the screws 15, andthe primary seal means in this example comprises a gland seal 32including a sealing ring 32A.

The jointing (splicing) operation is carried out as follows:

Prior to preparation of the cable sections 2 the appropriate parts areplaced over the respective cable section and in the following sequence:end cap 19 and then end plug 3. The casing 17 can be placed over any oneof the two sections 2. The following description relates generally tothe operation at one end of the joint; the operation at the other end issimilar. The cable end is now prepared for splicing by removing a lengthof the outer sheath 23 (see FIG. 7) taking care not to disrupt the coreformation 24 as this will make the placing of the end plug difficult andcould cause damage to the insulation of the conductors contained in thecable. The cable core 24 is now fed through the metal sleeve 11 of theplug and the cable sheath 23 fully inserted into the slot 12 so that thesleeve 11 is placed between the sheath 23 and the core shield (notshown) to provide screen continuity.

The spacer tubes 16 are now placed in position joining both end plugs 3,and secured by the socket screws 15. As will be noted, the axial lengthof the tubes 16 is significant since it controls the marriage of the endplug 3 to the main sleeve or casing 17 by means of the double threadedend cap 19.

The conductor pairs of the cable sections 2 are now ready for splicing,and splicing is facilitated by the hand tool so leaving the hands freefor the splicing operation. When splicing has been completed, the casing17 is positioned between the end plug 3 and secured by the end caps 19which are screwed onto the casing 17 and into the end plug 3 in the sameoperation. Final tightening of the end cap 19 should be done using twostrap wrenches, one to hold the casing 17 and the other to tighten theend cap 19. The locating ring 25 and keys 26 prevent relative movementbetween casing 17 and end plug 3 during the tightening operation.

To re-enter the joint at any time only the end caps 19 need be unscrewedto enable the casing 17 to be pushed aside; the primary seal means andscreen continuity will remain in position untouched. The rigid nature ofthe sleeve 11 will ensure effectiveness of the primary seal means. Theabove splice joint provides the additional significant advantage of thesheath not having to be brought into the splicing area, since the sheathend is located in the slot 12. By this arrangement the possibility ofsplice failure due to ingress of moisture is virtually ruled out.Modifications are of course possible. Thus, for example, only one end ofthe joint may conform to the arrangement shown in FIG. 2. Also thecasing may only have a single entry i.e. the other end may be blind.

The above description relates only to the joining of the sections of asingle cable; however by providing the end plug 3 with two or morespaced bores each with axial wall projections, the jointing of two ormore cables is possible in the single jointing apparatus. Also, thebores may be initially blind and are subsequently cut to provide throughbores only when required for use. While the example describes apparatusfor the splice joint for a telecommunication cable, it is alsoapplicable to an electrical cable and substantally similar apparatuscould be used for the connection of conduits in gas and water pipesystems; in this case it would probably not be necessary to include theauxiliary sleeve 11.

The primary seal means selected for use with fibre optic cables andprimary or main cables is preferably provided by a jointing compoundbetween the wall 6 and the relevant cable section obtained by injectionwelding; with secondary cables and cable T.V. cables a heat shrinkablecollar is preferably fitted over the end of the wall 6 and heat shrunkonto the cable section; and with fluid pipes, the wall 6 preferably hasan external screw thread 8 to receive a sealing gland nut 32A (FIG. 7)to be tightened thereonto, a gland seal of a silicone rubber O-ring 33being located to be tightened against the conduit section.

The end caps are preferably provided with an annular channel 28 to be inregistry with a bore 29 provided in a shoulder 30 of the casing 17 asshown. A security bolt 31 is screwed into bore 29 and impinges into thewalls of the channel to hold the cap in position against unauthorisedentry.

We claim:
 1. Sealed jointing apparatus for use in the connection ofconduit sections comprising an annular casing having open ends; spacedend closures at the ends of the casing, and defining with the casing aconnection zone into which conduit sections pass for jointing; andreleasable securing means for releasably securing at least one of theend closures to the casing; said releasable securing means comprising anend cap having an aperture and including two radially spaced couplingthreads, one of which coupling threads threadingly engages an externalthread on the casing while the other coupling thread engages an internalthread on said at least one end closure whereby the casing is releasablycoupled to said at least one end closure.
 2. Apparatus as claimed inclaim 1, wherein alignment means are provided for relative positioningof said internal and external threads to facilitate screw fitment of theend cap onto said at least one end closure and the casing.
 3. Apparatusas claimed in claim 1, wherein the end closures comprise annularmembers.
 4. Apparatus as claimed in claim 1, wherein an end closureincludes a closed-bottom annular slot concentric with the respectiveaperture to receive a sheath portion of a sheath encased cable section.5. Apparatus as claimed in claim 4, wherein the at least one end closurecomprises an annular member and a rigid axially-extending auxiliarysleeve arranged to form with the annular member said closed bottomannular slot.
 6. Apparatus as claimed in claim 5, wherein the sleeve isof metal and serves to provide screen continuity for conduit sectionscomprising a telecommunication cable.
 7. Apparatus as claimed in claim1, wherein a primary seal means is provided in the form of a gland sealcarried by an end closure.
 8. Apparatus as claimed in claim 2, whereinsaid alignment means comprises an indexing ring having indexing elementsthereon, aperture means being provided in the casing and in said atleast one end closure to receive said indexing elements.
 9. Apparatus asclaimed in claim 1, wherein spacer means extend between the end closuresand serve to axially space the end closures by a predetermined amount.10. Apparatus as claimed in claim 9, wherein the spacer means comprisesat least two rods.